People living in sub-Saharan Africa are less likely to be adherent to their antiretroviral treatment (ART) than people living in Asia, according to research comparing adherence patterns between the two regions.

While adherence was generally good across both regions – 4.8% of people in Asia had suboptimal adherence compared to 7.3% people in Africa – the authors note that the difference in adherence patterns could be the result of weaker health systems in Africa and different psychosocial and lifestyle factors between the regions.

Ensuring people take their HIV treatment as prescribed is an integral part of the delivery of successful HIV treatment programmes. Antiretroviral drugs work by suppressing the level of virus in the body to the point where it is at an undetectable level.

If a person does not take daily treatment as prescribed, the virus has a chance to rebound in the presence of antiretroviral drugs, likely resulting in drug resistance and disease progression.

The analysis focused on 3,934 people starting antiretroviral treatment, of whom 62% were from sub-Saharan Africa and 38% from Asia. Low- and lower-middle income countries made up 52% of the participants, with 48% from upper-middle or high-income countries.

Viral load and adherence assessments were conducted at base, 12 months and 24 months. The proportion of patients with viral suppression remained at 90% over the three follow-up points in Africa, and 94%, 96% and 95% in Asia.

In Africa, suboptimal adherence was independently associated with being male, younger, using other medicines and attending a public health facility. In Asia, men who have sex with men (MSM) tended to adhere better to their treatment, while people with a history of injecting drug use were less adherent.

More generally, lower income country status was independently associated with suboptimal adherence, likely the result of poor national health systems. This is confirmed in the differences in the regions, where Asian health systems are generally better equipped than those in sub-Saharan Africa.

In sub-Saharan Africa itself, participants who attended private clinics fared much better in adhering to their drugs than those attending a public clinic.

Well-resourced clinics are more likely to provide viral load testing, a major indicator of treatment adherence and success. In Africa, while patient-specific factors were reported for non-adherence - such as stigma, depression, sickness, scheduling demands and forgetfulness - pharmacy drug stock outs were also a frequently reported reason for not being able to take treatment.

In both regions, the longer a person was on treatment the more likely they were to be adherent, particularly in Africa. Care attrition is more common in low- and middle-income countries, particularly at the early stages after treatment because of loss to follow-up and early mortality.

But even when this was accounted for, adherence improved over time, likely the result of patients getting used to taking their drugs, early side effects disappearing and counselling and adherence support.

The authors note that interventions should focus on patient-reported barriers to treatment adherence, emphasising the first few years after treatment initiation as a critical component of the scale-up of antiretroviral treatment access.